The overall goal of the proposed studies is to establish environmental conditions that optimize the health of mice used in biomedical research, provide a safe and comfortable workplace, and minimize the costs associated with doing animal-based research. The methods by which the applicants will approach this goal include: (1) determining housing conditions that minimize pathogen transfer, (2) evaluating effects of culling on reproductive success, (3) identifying husbandry and hygiene practices that reduce caretaker exposure to mouse allergen, and (4) instituting workplace activities that may improve the health of animal caretakers. The investigators will first study the capacity of ventilated caging maintained at "neutral" airflow and negatively ventilated changing tables to reduce worker exposure to allergen and to reduce or eliminate transfer of Pasteurella pneumotropica, Helicobacter spp. and Pneumocystis carinii from infected mice to pathogen-free immunocompromised mice. The applicants will determine reproductive success of mice whose litters are culled or not and housed under different ventilation conditions. The efficacy of water, dilute tannic acid, and dilute sodium hypochlorite used to reduce breathing zone allergen levels during bedding changes will be tested. Skin and clothing of caretakers will be sampled for Staphylococcus aureus upon entry into mouse rooms through air or wet showers and for allergen upon exiting the facility through air or wet showers. In an effort to reduce employee workplace injuries, a functional capacity checklist will be developed and will be used to design an employee exercise program. Lastly, a pre-employment Functional Capacity Assessment tool to help slot new hires in positions for which they are physically capable will be used.